This invention relates to a method for purifying dialysing liquids used in hemodialysis processes. In particular the invention relates to the removal of phosphate ions from these dialysing liquids.
Hemodialysis processes, i.e. processes for purifying human blood by dialysis, have recently been studied in which the dialysing liquid is continuously recycled after passing through a purification or regeneration stage. In the regeneration stage the toxins originating from the blood, the most important of which are urea, ureic acid, creatinine etc. are removed from the dialysing liquid. Although the presence of phosphate ions is also harmful to the human body, the removal of these ions has been relatively ignored in the dialysing liquid regeneration methods used up to the present time.
The need to remove phosphate ions from the blood derives from the fact that these ions displace the calcium and magnesium from the body to a harmful level, giving rise to the dangerous phenomenon of decalcification of the osseous system. As the proper transfer of phosphate ions from the blood to the dialysing liquid is dependent upon low concentration of these ions in this latter, it is necessary to remove substantially 80% of the phosphate ions from the dialysing liquid before recycling it to the hemodialysis process.
In known dialysing liquid purification processes the phosphate ions have been eliminated by absorption on activated carbon, together with other toxins of an organic nature. The main disadvantage of these methods is the poor capacity of activated carbon to retain the phosphate ions. It has been attempted to replace the activated carbon by other absorbents more effective in removing phosphate ions, such as zirconium oxide. These absorbents however have been shown to be just as disadvantageous in that in addition to the phosphate they remove substantial quantities of calcium, magnesium and potassium ions, so destroying the required electrolytic equilibrium of the dialysing liquid. It is therefore necessary in such purification systems to continuously infuse calcium, magnesium and possibly potassium into the dialysing liquid before recycling it to the dialysis process.
However these requirements lead to considerable clinical complications, and make the entire hemodialysis process difficult to carry out.